On Thu, Dec 29, 2011 at 01:39:06PM +0100, Marek Szyprowski wrote:
> From: Michal Nazarewicz <[email protected]>
>
> The MIGRATE_CMA migration type has two main characteristics:
> (i) only movable pages can be allocated from MIGRATE_CMA
> pageblocks and (ii) page allocator will never change migration
> type of MIGRATE_CMA pageblocks.
>
> This guarantees (to some degree) that page in a MIGRATE_CMA page
> block can always be migrated somewhere else (unless there's no
> memory left in the system).
>
> It is designed to be used for allocating big chunks (eg. 10MiB)
> of physically contiguous memory. Once driver requests
> contiguous memory, pages from MIGRATE_CMA pageblocks may be
> migrated away to create a contiguous block.
>
> To minimise number of migrations, MIGRATE_CMA migration type
> is the last type tried when page allocator falls back to other
> migration types then requested.
>
> Signed-off-by: Michal Nazarewicz <[email protected]>
> [m.szyprowski: removed CONFIG_CMA_MIGRATE_TYPE]
> Signed-off-by: Marek Szyprowski <[email protected]>
> Signed-off-by: Kyungmin Park <[email protected]>
> ---
> include/linux/mmzone.h | 41 ++++++++++++++++++++----
> include/linux/page-isolation.h | 3 ++
> mm/Kconfig | 2 +-
> mm/compaction.c | 11 +++++--
> mm/page_alloc.c | 68 ++++++++++++++++++++++++++++++---------
> mm/vmstat.c | 1 +
> 6 files changed, 99 insertions(+), 27 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 188cb2f..e38b85d 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -35,13 +35,35 @@
> */
> #define PAGE_ALLOC_COSTLY_ORDER 3
>
> -#define MIGRATE_UNMOVABLE 0
> -#define MIGRATE_RECLAIMABLE 1
> -#define MIGRATE_MOVABLE 2
> -#define MIGRATE_PCPTYPES 3 /* the number of types on the pcp lists */
> -#define MIGRATE_RESERVE 3
> -#define MIGRATE_ISOLATE 4 /* can't allocate from here */
> -#define MIGRATE_TYPES 5
> +enum {
> + MIGRATE_UNMOVABLE,
> + MIGRATE_RECLAIMABLE,
> + MIGRATE_MOVABLE,
> + MIGRATE_PCPTYPES, /* the number of types on the pcp lists */
> + MIGRATE_RESERVE = MIGRATE_PCPTYPES,
> + /*
> + * MIGRATE_CMA migration type is designed to mimic the way
> + * ZONE_MOVABLE works. Only movable pages can be allocated
> + * from MIGRATE_CMA pageblocks and page allocator never
> + * implicitly change migration type of MIGRATE_CMA pageblock.
> + *
> + * The way to use it is to change migratetype of a range of
> + * pageblocks to MIGRATE_CMA which can be done by
> + * __free_pageblock_cma() function. What is important though
> + * is that a range of pageblocks must be aligned to
> + * MAX_ORDER_NR_PAGES should biggest page be bigger then
> + * a single pageblock.
> + */
> + MIGRATE_CMA,
> + MIGRATE_ISOLATE, /* can't allocate from here */
> + MIGRATE_TYPES
> +};
MIGRATE_CMA is being added whether or not CONFIG_CMA is set. This
increases the size of the pageblock bitmap and where that is just 1 bit
per pageblock in the system, it may be noticable on large machines.
> +
> +#ifdef CONFIG_CMA
> +# define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
> +#else
> +# define is_migrate_cma(migratetype) false
> +#endif
>
Use static inlines.
> #define for_each_migratetype_order(order, type) \
> for (order = 0; order < MAX_ORDER; order++) \
> @@ -54,6 +76,11 @@ static inline int get_pageblock_migratetype(struct page
> *page)
> return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);
> }
>
> +static inline bool is_pageblock_cma(struct page *page)
> +{
> + return is_migrate_cma(get_pageblock_migratetype(page));
> +}
> +
This allows additional calls to get_pageblock_migratetype() even if
CONFIG_CMA is not set.
> struct free_area {
> struct list_head free_list[MIGRATE_TYPES];
> unsigned long nr_free;
> diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
> index d305080..af650db 100644
> --- a/include/linux/page-isolation.h
> +++ b/include/linux/page-isolation.h
> @@ -37,4 +37,7 @@ extern void unset_migratetype_isolate(struct page *page);
> int alloc_contig_range(unsigned long start, unsigned long end);
> void free_contig_range(unsigned long pfn, unsigned nr_pages);
>
> +/* CMA stuff */
> +extern void init_cma_reserved_pageblock(struct page *page);
> +
> #endif
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 011b110..e080cac 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -192,7 +192,7 @@ config COMPACTION
> config MIGRATION
> bool "Page migration"
> def_bool y
> - depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
> + depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA
> help
> Allows the migration of the physical location of pages of processes
> while the virtual addresses are not changed. This is useful in
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 8733441..46783b4 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -21,6 +21,11 @@
> #define CREATE_TRACE_POINTS
> #include <trace/events/compaction.h>
>
> +static inline bool is_migrate_cma_or_movable(int migratetype)
> +{
> + return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
> +}
> +
That is not a name that helps any. migrate_async_suitable() would be
marginally better.
> /**
> * isolate_freepages_range() - isolate free pages, must hold zone->lock.
> * @zone: Zone pages are in.
> @@ -213,7 +218,7 @@ isolate_migratepages_range(struct zone *zone, struct
> compact_control *cc,
> */
> pageblock_nr = low_pfn >> pageblock_order;
> if (!cc->sync && last_pageblock_nr != pageblock_nr &&
> - get_pageblock_migratetype(page) !=
> MIGRATE_MOVABLE) {
> + is_migrate_cma_or_movable(get_pageblock_migratetype(page)))
> {
> low_pfn += pageblock_nr_pages;
> low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
> last_pageblock_nr = pageblock_nr;
I know I suggested migrate_async_suitable() here but the check may
not even happen if CMA uses sync migration.
> @@ -295,8 +300,8 @@ static bool suitable_migration_target(struct page *page)
> if (PageBuddy(page) && page_order(page) >= pageblock_order)
> return true;
>
> - /* If the block is MIGRATE_MOVABLE, allow migration */
> - if (migratetype == MIGRATE_MOVABLE)
> + /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
> + if (is_migrate_cma_or_movable(migratetype))
> return true;
>
> /* Otherwise skip the block */
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 47b0a85..06a7861 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -722,6 +722,26 @@ void __meminit __free_pages_bootmem(struct page *page,
> unsigned int order)
> }
> }
>
> +#ifdef CONFIG_CMA
> +/*
> + * Free whole pageblock and set it's migration type to MIGRATE_CMA.
> + */
> +void __init init_cma_reserved_pageblock(struct page *page)
> +{
> + unsigned i = pageblock_nr_pages;
> + struct page *p = page;
> +
> + do {
> + __ClearPageReserved(p);
> + set_page_count(p, 0);
> + } while (++p, --i);
> +
> + set_page_refcounted(page);
> + set_pageblock_migratetype(page, MIGRATE_CMA);
> + __free_pages(page, pageblock_order);
> + totalram_pages += pageblock_nr_pages;
> +}
> +#endif
>
> /*
> * The order of subdivision here is critical for the IO subsystem.
> @@ -830,11 +850,10 @@ struct page *__rmqueue_smallest(struct zone *zone,
> unsigned int order,
> * This array describes the order lists are fallen back to when
> * the free lists for the desirable migrate type are depleted
> */
> -static int fallbacks[MIGRATE_TYPES][MIGRATE_TYPES-1] = {
> +static int fallbacks[MIGRATE_PCPTYPES][4] = {
> [MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,
> MIGRATE_RESERVE },
> [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE,
> MIGRATE_RESERVE },
> - [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE,
> MIGRATE_RESERVE },
> - [MIGRATE_RESERVE] = { MIGRATE_RESERVE, MIGRATE_RESERVE,
> MIGRATE_RESERVE }, /* Never used */
> + [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE,
> MIGRATE_CMA , MIGRATE_RESERVE },
Why did you delete [MIGRATE_RESERVE] here? It changes the array
from being expressed in terms of MIGRATE_TYPES to being a hard-coded
value. I do not see the advantage and it's not clear how it is related
to the patch.
> };
>
> /*
> @@ -929,12 +948,12 @@ __rmqueue_fallback(struct zone *zone, int order, int
> start_migratetype)
> /* Find the largest possible block of pages in the other list */
> for (current_order = MAX_ORDER-1; current_order >= order;
> --current_order) {
> - for (i = 0; i < MIGRATE_TYPES - 1; i++) {
> + for (i = 0; i < ARRAY_SIZE(fallbacks[0]); i++) {
> migratetype = fallbacks[start_migratetype][i];
>
> /* MIGRATE_RESERVE handled later if necessary */
> if (migratetype == MIGRATE_RESERVE)
> - continue;
> + break;
>
> area = &(zone->free_area[current_order]);
> if (list_empty(&area->free_list[migratetype]))
> @@ -949,11 +968,18 @@ __rmqueue_fallback(struct zone *zone, int order, int
> start_migratetype)
> * pages to the preferred allocation list. If falling
> * back for a reclaimable kernel allocation, be more
> * aggressive about taking ownership of free pages
> + *
> + * On the other hand, never change migration
> + * type of MIGRATE_CMA pageblocks nor move CMA
> + * pages on different free lists. We don't
> + * want unmovable pages to be allocated from
> + * MIGRATE_CMA areas.
> */
> - if (unlikely(current_order >= (pageblock_order >> 1)) ||
> - start_migratetype ==
> MIGRATE_RECLAIMABLE ||
> - page_group_by_mobility_disabled) {
> - unsigned long pages;
> + if (!is_pageblock_cma(page) &&
> + (unlikely(current_order >= pageblock_order / 2) ||
> + start_migratetype == MIGRATE_RECLAIMABLE ||
> + page_group_by_mobility_disabled)) {
> + int pages;
> pages = move_freepages_block(zone, page,
>
> start_migratetype);
>
> @@ -971,11 +997,14 @@ __rmqueue_fallback(struct zone *zone, int order, int
> start_migratetype)
> rmv_page_order(page);
>
> /* Take ownership for orders >= pageblock_order */
> - if (current_order >= pageblock_order)
> + if (current_order >= pageblock_order &&
> + !is_pageblock_cma(page))
> change_pageblock_range(page, current_order,
> start_migratetype);
>
> - expand(zone, page, order, current_order, area,
> migratetype);
> + expand(zone, page, order, current_order, area,
> + is_migrate_cma(start_migratetype)
> + ? start_migratetype : migratetype);
>
> trace_mm_page_alloc_extfrag(page, order, current_order,
> start_migratetype, migratetype);
> @@ -1047,7 +1076,10 @@ static int rmqueue_bulk(struct zone *zone, unsigned
> int order,
> list_add(&page->lru, list);
> else
> list_add_tail(&page->lru, list);
> - set_page_private(page, migratetype);
> + if (is_pageblock_cma(page))
> + set_page_private(page, MIGRATE_CMA);
> + else
> + set_page_private(page, migratetype);
> list = &page->lru;
> }
> __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
> @@ -1308,8 +1340,12 @@ int split_free_page(struct page *page)
>
> if (order >= pageblock_order - 1) {
> struct page *endpage = page + (1 << order) - 1;
> - for (; page < endpage; page += pageblock_nr_pages)
> - set_pageblock_migratetype(page, MIGRATE_MOVABLE);
> + for (; page < endpage; page += pageblock_nr_pages) {
> + int mt = get_pageblock_migratetype(page);
> + if (mt != MIGRATE_ISOLATE && !is_migrate_cma(mt))
> + set_pageblock_migratetype(page,
> + MIGRATE_MOVABLE);
> + }
> }
>
> return 1 << order;
> @@ -5599,8 +5635,8 @@ __count_immobile_pages(struct zone *zone, struct page
> *page, int count)
> */
> if (zone_idx(zone) == ZONE_MOVABLE)
> return true;
> -
> - if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE)
> + if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE ||
> + is_pageblock_cma(page))
> return true;
>
> pfn = page_to_pfn(page);
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 8fd603b..9fb1789 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -613,6 +613,7 @@ static char * const migratetype_names[MIGRATE_TYPES] = {
> "Reclaimable",
> "Movable",
> "Reserve",
> + "Cma",
> "Isolate",
> };
>
> --
> 1.7.1.569.g6f426
>
--
Mel Gorman
SUSE Labs
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